A compressor generally includes a diffuser for reducing the speed of a fluid disposed downstream of the outlet side of an impeller to convert the dynamic energy into a static pressure. Some compressors include diffusers with variable geometry, for example, in the form of adjustable diffuser vane angles. A variable diffuser is used for aerodynamically sizing the flow through the compressor with the aim of minimizing flow losses. However, currently, speed control in compressors is based on a single point diffuser setting. Disadvantageously, this leads to an increase in power consumption and/or reduction in efficiency of the compressor when the diffuser setting is changed.
The documents EP 0 186332 A1, WO 2006/017365 A2 and EP 0 761 981 A2 deal with a method of the incipiently mentioned type.